1. Field of the Invention
The embodiments of the invention generally relate to reuse of previously processed wafers, and, more particularly, to an improved process that uses particle application to remove patterned structures from wafers without removing significant amounts of silicon from the wafers.
2. Description of the Related Art
Large amounts of money are spent every year on silicon wafers that are used to monitor manufacturing operations. To reduce such costs, the monitoring wafers can be sold, recycle, or reclaimed. One issue is that the circuit patterns on the wafers (be it product or monitor wafers) is proprietary and should not be sent out to vendors for rework or sale.
One solution to removing such patterns is a prolonged exposure in a wet bath (such as HF, HNO3, H2O2, S, P, HCL, etc.). While this wet bath process does indeed remove all films, it often causes significant bulk silicon removal as well, since the materials being removed are similar in characteristics to silicon. Further, the non-uniform film coverage creates non-uniform etch spots. The resulting wafer product of such wet bath processing is a highly stress lattice and is fragile wafer after a rework cycle. Also, the costs of such processing are increased by the dedicated wet tank that is needed, the cost of the chemicals that are needed, and the need to dispose of the used chemicals.
Another method for removing patterned structures performs a layer by layer removal process. In such a process, each layer is removed (one at a time) using specific wet chemistry combined with dry etching. While such processing minimizes silicon substrate damage, it has high costs including the requirement for dedicated tools. Further, such processing is time and labor intensive and involves lapping and grinding.
In addition, such layer by layer processing can cause lattice damage causing wafers to break and requires post-processing polishing.